1. Field
This application generally relates to wireless user equipment, such as wireless devices that use wireless signals to determine the location of devices such as cell phones.
2. Background Information
Wireless cell phones have become almost universal in the modern world. The primary purpose of cell phones was, and still is, to provide wireless voice communication services. However, data communication is becoming increasingly important, and a host of additional features are being implemented in cell phones.
When adding features to a cell phone, the effect upon system performance must be considered. Additional features increase the load upon the cell phone's system, decreasing system performance.
The computing system of a cell phone is limited in size, capacity, and battery power. In order to make efficient use of its limited resources, the cell phone may communicate with other network resources using its communication capabilities; in other words, the cell phone may “off-load” some of its computationally intensive tasks to servers with much greater computation capabilities. For example, some position location functions may be performed by a dedicated server, such as a Position Determination Entity (PDE). To aid the location measurements, the PDE may provide assistance data to the cell phone. However, the assistance data is usually generalized for a wide range of conditions, and therefore under some circumstances may not be useful, or just not fully optimized.
Some cell phone operations are more efficiently performed by the cell phone, and still other functions must by necessity be performed by the cell phone itself. One such required function is actual position location data collection. In handset-based position location technologies, the wireless device carries out the fundamental location measurements. These position location operations can be particularly demanding upon system performance; for example, an attempted location fix may consume several seconds or more, during which time the phone's communication functionality may be diminished. Such periods of temporary diminished functionality can be very annoying and potentially disruptive to a user whose ability to make or receive a phone call during this period may be affected.
In all handset-based position location technologies, location measurements are made by the user equipment (UE). Measurements may be made of signals from base stations or GPS satellites, or signals from any other location reference sources. In the most efficient handset-based position location solutions, wireless assistance is provided to the handset from a wireless network; particularly, the network sends assistance data to the user equipment (UE) aimed at increasing the signal detection reliability and/or decreasing the time required for completing the measurements. Conventional assistance data may include a variety of information, such as a list of visible signal sources, information indicating the expected code phase, the code phase window size, the signal Doppler, and the Doppler window size. One type of assistance data provides information about the signal modulation, for example the assistance data could provide the sequence of modulation bits.